The initial meeting of these two groups was probably not quite as calm and easy as Mormon makes it appear. If Gideon's men had come to kill the king, they would be ready for a fight. The returning men would be tired and exhausted, but perhaps not immediately certain that they had met with a Nephite party or a Lamanite party. When they were close enough to see clearly, surely there would have been recognition of at least some who knew each other.
Clearly the returning men would be anxious for their abandoned families, and they learn of the fate of those families, as well as the entire city.